The 20 Year Super Mesh Safety Cover is one of our best mesh covers available and has a few unique features: The Super Mesh cover blocks 99% of sunlight making it nearly impossible for algae to grow, this will make your spring cleanup easier than ever! Although the tight weave blocks 99% of UV rays, the Super Mesh cover still allows water and melted snow through the cover giving you optimum drainage and safety while keeping debris out! The Super Mesh cover is best for mild and moderate Winter climates with moderate snowfall.